Domain walls detection in a single magnetic ring by MR measuring

We demonstrated the results of the MR measurement in a single magnetic ring. The measurement was performed at room temperature with applying magnetic fields of constant magnitudes in the direction of the ring plane, while rotating the magnetic ring in its plane. The anisotropic field of the narrow ring forces the local moment aligned to the direction of perimeter of the ring, hence the onion state forms. Besides, the field of 250 Gauss can still drag the 2 domain walls at the onion state along the perimeter of the ring without changing the direction of other local moment which is not in the region of the 2 domain walls. While the first domain wall dragged into the region between voltage contacts, the local moment in this region is no longer parallel to the perimeter of the ring, hence a drop appears (or the resistance decreases). With sharp drops, the rotating MR measurement can be used to detect domain walls.